The present invention relates to methods of treating onychomycosis employing compositions with a combination of urea and an antioxidant. Onychomycosis refers to a fungal infection of the nail unit, defined as the nail matrix, bed or plate.
Urea has been long recognized as a cosmetic ingredient in formulations acting as a humectant and moisturizer. High concentrations of urea, such as 40%, are also known to have mild, antimicrobial effect. At these strengths the antibacterial effects are said to be similar to those of antibiotics, with the further advantage that all the common organisms are susceptible and the possibility of resistant strains need not be seriously considered. There have been reports of keratolytic activity attributed to urea with the ability at high concentrations to solubilize and denature protein. Dermatological compositions containing from 21 to 40 wt-% urea for treating dry scaly skin have been described in U.S. Pat. No. 5,919,470.
Fungal infections of the nail are notoriously difficult to treat. Traditional, topical therapies cannot penetrate the nail plate, and eradicate the infection in and under the nail bed; they are useful only in milder forms of the disease. Systemic antifungal drug therapy is associated with potentially harmful side effects. Since oral antifungals are distributed throughout the entire body, systemic side effects such as elevated liver enzymes, gastrointestinal disorders and skin rashes are not uncommon and may require expensive medical intervention and laboratory tests.
Topical formulations for treating fungal infections, such as onychomycosis, have been described in U.S. Pat. No. 6,281,239B1. The method employs the use of a combination of a known antifungal agent and a tissue softening composition containing 30 to 60 wt-% urea.
We have recently found urea to be useful as the sole active ingredient in topically treating onychomycosis. This has been described in our co-pending application Ser. No. 10/103,213 of Mar. 20, 2002, which is incorporated herein by reference.
As the outermost layer of skin, the stratum corneum (SC) is continuously exposed to an oxidative environment, including air pollutants, ultraviolet radiation, chemical oxidants, and aerobic microorganisms. Human SC reveals characteristic antioxidant and protein oxidation gradients with increasing antioxidant depletion and protein oxidation towards the outer layers. SC antioxidants, lipids, and proteins are oxidatively modified upon treatments with ultraviolet A/ultraviolet B, ozone, and benzoyl peroxide. Thiele J. J., Schroeter C., Hsieh S. N., Podda M., Packer L., Curr Probl Dermatol. 2001;29:26-42.
Furthermore, the skin is increasingly exposed to ambient UV-irradiation thus increasing its risk for photooxidative damage with long term detrimental effects like photoaging, which is characterized by wrinkles, loss of skin tone, and resilience. Scharffetter-Kochanek K, Brenneisen P, Wenk J, et al., Exp Gerontol. 2000; 35:307-316
We have also recently described in a co-pending application topical products containing a combination of an antioxidant and a high concentration of urea which provide added efficacy and suitability for treating and protecting skin. Co-pending application Ser. No. 09/998,537 of Nov. 28, 2001 is incorporated herein by reference.
The present invention relates to methods of treating onychomycosis employing compositions containing urea as the antifungal agent. The present invention relates to methods for treating onychomycosis in humans using a combination of a safe and effective amount of urea, and from about 0.1 to about 20 wt-% of an antioxidant in a suitably defined formulation. These methods include topically administrating to the nail area of a human a safe and effective amount of the above combination. Onychomycosis refers to a fungal infection of the nail unit, defined as the nail matrix, bed or plate.
Accordingly, the present invention is a method for treating onychomycosis by topically administering a composition containing from about 10 to about 60 wt-% urea; from about 0.1 to about 20 wt-% of an antioxidant, and the balance being dermatologically acceptable excipients.